This study in older men and women tests two hypotheses: (i) the insulin- like growth factor, IGF, suppresses growth hormone (GH) less in the presence of sex-steroid hormones than in their absence; and (ii) sex- steroid hormones increase the metabolic clearance rate of IGF-I, but not GH. Low dose IGF-I fails to suppress GH in women (5 evaluated). We are completing assessment of the corresponding protocol in men.